Enameling furnace



May 10, 1932- R. M DOUGALL ENAMELING FURNACE Filed Sept. 10, 1928 8 Sheets-Sheet 1 mnuva rams:

0y, macr May 10,. 1932. MacDQUGALL ENAMELING FURNACE Filed Sept. .10, 1.928

18 Sheets-Sheet 2 u m R mmmmmmmwwww May 10, 1932. MacDOUGALL ENAMELING FURNACE Filed Sept. 10, 1928 8 Sheets-Sheet 3 May 10, 1932. MacDOUGALL. 1,857,206

ENAMELING FURNACE Filed Sept 10, 1923 a-sneets-sheet 4 May. 10, 1932. R, MacDQUGALL ENAMELING FURNACE Filed Sept. 10. 1928 8 Sheets-Sheet 5 May 10, 1932. MacDOUGALL 1,857,206

ENAMELING FURNACE Filed Sept. 10, 1928 8 Sheets-Sheet 6 R. M DOUGALL ENAMELING FURNACE Filed Sept. 10, 1928 8.Sh.e ts-Shee t 7 m we @, fldmwwp may 10, 19.32.- R. MacDQUGALL 1,857,206

ENAMELING FURNACE Wig Patented May 10, 1932 UNITED STATES PATENT OFFICE ROBERT MACDOUGALL, OF DOWNEBS GROVE, ILLDTOIS, ASSIGNOB TO BEEHACK FUR- NACE COMPANY, OF CIOERO, ILLINOIS, A CORPORATION OF ILLINOIS ENAKELIN G FURNACE My invention relates to improvements in a furnace adapted particularly for drying and fusing a coating of vitrifiable materials which has been applied in the form of a thin aqueous paste to sheet metal articles such as kitchen utensils and similar articles, to produce an adherent vitrified enamel covermg. The eneral construction of the furnace may be. similar to that shown in Patents Nos. 1,603,014 and 1,603,015, both dated October 12, 1926, and relating to inventions jointly made by myself and Herbert G. Beasley. The object of my invention is to improve the construction disclosed in said patents in certain respects relating to the arrangement and construction of the burning, and preheating, and drying chambers; to the provision of auxiliary drying chambers to the mechanical construction of a muflle wall separating the combustion chamber and the burning chambers; to a device for controlling objectionable circulation and preheating of hot air out of the open end of the furnace and cold air into the same; and to a novel improved construction of the conveyor chain and carriers thereon employed for supporting articles passing through the furnace. In the appended claims I have more particularly pointed out the essential elements of my invention without intention of limiting them to the particular mechanical construction hereinafter described, and illustrated in the accompanying drawings, except in so far as the terms employed serve to distinguish my invention from the prior art.

In the accompanying drawings '1 have illustrated in Figure 1, for purposes of exposition and explanation on a small scale and in plan view. an enameling furnace and associated apparatus in which my invention is embodied;

Fig. 2 is a side view of the same;

Fig. 3 is a plan view on a larger scale of the opposite ends of the conveyor apparatus;

Figs. 4 and 5 are respectively a plan view and a side view of the furnace on a scale inter-. mediate the scales of Figs. 1 and 3.

Fig. 6 is a horizontal section of the main furnace roper;

Figs. and 8 are transverse vertical sections on a larger scale of the drying chambers of an auxlliary drying furnace in planes indicated by the dotted lines 77 and 8-8 respectively of Fig. 4;

Fig. 9 is a side view of the portion of the auxiliary furnace illustrated in Fig. 8;

Fig. 10 is a fragmentary transverse vertical section of a portlon of the furnace on the dotted line 10-10 of Fig. 11;

Fig. 11 is a section in a 1plane indicated by the dotted line 11-11 of ig. 10;

Fig. 12 is a top plan view of the metallic muflle member shown in Figs. 10 and 11, detached;

Fig. 13 is a front view of a draft-controlling device at one end of the furnace;

Fig. 14 isa top plan view of the same;

Fig. 15 is a central horizontal section of the same, viewed as indicated by the arrow and dotted line 15-15 of Fig. 14;

Fig. 16 is a perspective of the top member of such draft controlling device detached;

b Fig. 17 is a perspective of the bottom mem- Fig. 18 is a crosssection, on the dotted line 1818 of'Fig. 6 and on a small scale of the furnace structure, the conveyor apparatus bein omitted;

ig. 19 is a longitudinal vertical sectlon, on a small scale, of the central portion of the main furnace, broken in a plane indicated by the dotted line 1919 of Fig. 6;

Fig. 20 is a transverse vertical section of a top portion of the furnace, illustrating improvements in the conveyor apparatus;

Fig. 21 is a section on the broken line 2121 of Fig. 20, the principal conveyor members being shown in elevation Fig. 22 illustrates a carrier device of a form which is usually employed for supporting articles as'they pass through the sections of the main furnace, viewed ongitudinally of the furnace;

Fig. 23 is a view of the same, as seen at right angles to the furnace chambers;

Fig. 24 is a plan view of the same; a

Fig. 25 is a view of a modified form of carrier, which has been found particularl I adapted for use in conveying articles throng the auxiliary furnace;

Figs. 26 and 27 are respectively a perspective and a fragmentary section of a supporting'pin used for supporting certain classes of articles in the carrier devices illustrated in 22 to 25, inclusive; and

g. 28 is a detail showing a joint between certam baflling members.

Like reference characters indicate like parts in all the figures of the drawings.

As illustrated in the drawings,see more rticularly Fig. 1,-my present improved fi irnace, in the preferred embodiment, comprises a main furnace, which includes a central burning or vitrifying section A, preheating sections B and C at opposite ends of the burning section and preferably in alinement therewith, and drying sections D and E at the outer ends of the preheatin sections; auxiliary drying furnaces Fand at op 0- site sides of the main furnace and prefera ly pgrallel therewith; another auxiliary drying rna'ce H preferably in longitudinal alignment with the auxiliary furnace F and two driven conve or chains traveling in the same horizontal ane, ,one of which, marked 1, conveys articles to be enameled through one side of the chambers of the main furnace and through the auxiliary drying furnaces F and H and the other of which, marked 2, conveys articles through the other side of the main furnace in a. dlrection of travel opposite that of the chain 1, and through the auxiliary furnace G. a

The main furnace is formed with two separated parallel combustion chambers, one of which, indicated by'the reference numeral 3 (Fig. 6) extends on one side of a central par tition wall 4 of the furnace from the right end of the burning section A (usin terms indicating position as viewed in Flgs. 1 to 6 of the drawings) to near the middle of the preheating section B and the other of which, marked 5, on the other side of the central partition wall of the furnace extends from the left end of the section A to a point near the middle of the preheating section C. The combustion chamber 3 is heated in the present instance, by an oil burner 6 (though, of course, gas may be used as a fuel if desired) and the chamber 5 by a burner 7. The burning chambers 88 of the burning section A above the combustion chamber are separated from each other by the upper portion of the partition wall 4 above mentioned, and from the combustion chambers by muflle walls which will later be described in detail; and the remaining portions of the preheating sections B and C, are filled or built up solid to the plane of the muflle chambers, as are also the drying sections D and E. Above the plane of the muflie walls,and of the top of the solidly built-upsections B and C and the similarly built-up sections D and E,the preheating sections are partially separated by a central line of supporting columns 9, somewhat closely spaced, and the drying sections are separated to a less extent by more widely spaced supporting columns 10.

The partition wall 4, which separates the two burning chambers 8, 8 permits the maintenance of different temperatures therein, so that the finishing coat can be fused at a lower temperature than the ground coat in accordance with well known practice. The provision of a line of supporting columns 9 between the other sections, as distinguished from continuous wall, permits of the transfer of heat to one side of the furnace from the other whereby the heat given off by outgoing articles is utilized in preheating incoming articles.

At the end of the combustion chamber 3 opposite the burner 6 such ch amber communicates through a transverse flue passage 11, formed, in the present instance, in a con necting wall, which communicates with a horizontal heating pipe 12 seated in a masoncombustion are carried off. Similarly, the

right end of the combustion chamber 5 communicates with a heating pipe 14 running along the bottom of the auxiliary drying furnace G and communicating with a chimney 15. For economy of construction the less strongly heated portion of the auxiliary furnace F may be formed with sheet metal side walls, instead of brickwork,--compare Figs. 7 and 8,and the auxiliary drying furnace H, which is heated by an independent oil burner, may be of similar construction.

Describing now the muflie partition structure hereinbefore referred to, it may first be stated that in the development of continuous enameling furnaces of the type above de-' scribed, carborundum mufiies have been found to give satisfactory results for only a short time while the furnace was new, due to the fact that this material has considerable expansion under heat, and while provision may be made for such expansion, the material will vitrify under high heat and the sections unite, after which it will shortly crack where weakest and the muffle then leak and admit products of combustion from the combustion chamber into the burning chamber and connected chambers above. To remedy these defects of previous furnaces I have devised my present novel muflie structurefithe curve of such arches, and at theirends resting u on horizontal faces of the furnace walls ad acent opposite ends of the arches, thus closing the openings between the jack arches. The plates 71 are severally formed with opposite ribs 72 on their under sides, a short distance inside their curved edges, and also with opposite depending cross-ribs 73 which serve to position them between the arches while providing for expansion, and also serve to strengthen them, and with cross ribs 74 on their upper faces which serve both to strengthen the plate and keep it from sagging under the intense heat to which it is subjected and also serve to support above the face of the body of the plate any articles which may happen to drop from the carrier boxes or conveyor structure traveling through the burning chamber above the mufile. If such ribs were not provided and a piece of ware should fall upon the face of the plate and cover say a space of half a square foot or so of surface, radiation would be retarded and the portion covered would rapidly overheat and probably burn through.

The carrier chains of my novel improved furnace are constructed in a simple and eflicient manner, with especial reference to protection against undue heating of the links of the chain and the upper ends ofithe suspension rods by means of which the articles to be enameled are transported through the burning chamber. The chains are each constructed,-see Figs. 20 and 21,of inner link members 16 and 16, both consisting of upper and lower plate sections connected by orificed hubs by means of which they are driven and are pivoted to intermediate pairs of outer link members 17. The lower plate sections of the inner link members 16 and 16 are formed with pivoting lugs to which are pivotally connected depending baflie plate members 34, which will later be referred to again.

The links 16, spaced at short intervals throughout the chain, are formed with suspension brackets 18 which at their upper ends are severally formed with hubs which pivotally support a pair of rollers 19-19 running upon tracks 2020 which are stationarily supported and extend between the sprocket wheels around which the two-chains severally travel. Within the vertical planes of the ends of the auxiliary furnaces (see Figs. 7, 8 and 9) the tracks may conveniently be secured within the sides of an inverted three-sided hood 21 open at the bottom extending down into the furnace chamber, and suspended from the under side of an I-beam 22 extending longitudinally above the center line of the furnace and secured to cross members 23 at the top of side posts 24 forming part of the metal frame work of the furnace. Intermediate the furnaces the tracks may be similarly supported within the side members of a shallower hood 25 (Fig. 1)

secured to an I-beam fixed to bracket arms 26 carried by the upper ends of posts 27 spaced at suitable distances apart.

The conveyor chain 1 is driven by means of a sprocket wheel 40 engaging the hubs of the inner link members 16 and 16 at the loop of the belt at the right end of the apparatus (viewed as in Figs. 1 to 6) and engages an idler guide roller 41, and at'the left end of the line of furnaces, a series of idler sprocket wheels (see Fig. 3), these idler sprocket wheels, marked respectively in order, 42, 43, 44, 45 and 46, being arranged in approximately a semi-circle of considerable radius, to avoid sharp bends in the line of travel and thereby provide suflicient clearance for articles on the chain between the carrier boxes later to be described, and to provide space between the two reaches of the chain for work stations therein. The center sprocket wheel 44, of the group is preferably mounted in bearings which are adjustable longitudinally of the line of apparatus, for the purpose of taking up slack in the chain.

The conveyor chain 2 may be constructed and supported in the same manner as chain 1, and in the present instance is engaged by a driving sprocket wheel 91, an adjustably mounted idler sprocket wheel 90, and two idler sprocket wheels 92 and-93. which guide the chain into and out of the auxiliary drying furnace G.

Within the planes of the opposite ends of the main furnace, the tracks 2020 of the two chains are secured to the inner faces of pairs of bracket plates 28,-see Figs. 20 and 21,-the pairs being severally bolted to cross frame members 29 on each side of two narrow tapering slots, marked 30, slightly wider at the bottom than the top, which severally extend on opposite sides of the top of the furnace centrally through the burning chamber on the particular side and the aligned portions of the preheating and drying sections of the furnace. Seated in the furnace wall at the upper end of each slot 30 are two opposite lines of baflling rails 31, formed with lugs also connected by bolts severally to the bracket plates 28. These bafliing'rails are preferably shouldered at their meeting ends, to provide mating joints, offset at top and bottom,see Fig. 28. Between the bracket plates and the track members and bafliing rails are secured thin three-sided sheet metal hood, members 32 which make telescopic sealed connection with hood members 33, providing an airtight conduit into which cool air under a slight degree of pressure is ad-' mitted at a point about midway between the ends of the furnace. as through pipe 33A shown in Fig. 21. While the ends of the air conduit are open there is suflicient pressure over the central part of the furnace, above the burning chamber and adjacent portions of the preheating chambers, to balance the tendthe slot below the plane of the bafiling rails,

The baflling rails 31 have the cross-sec- .tional form shown in Fig. 20, thus providing for a shouldered recess on each side of the slot 30 to receive upper flange portions'a'of the. bafile blocks 34 hereinbefore mentioned. These blocks are also formed with lower flanges b which extend between the sides of and the upper flanges are cut away at one end and extended at the other (see Fig. 21) so that in the assembled chain, rays of radiant heat from below are intercepted and direct passage of heated air through the ga' s between the blocks is prevented. The locks are also centrally orifi'ced and recessed to ermit insertion into seats therein of the hoo ed upper ends of suspension rods 35 which carry the skeleton carrier boxes employed to contain-and suspend the articles to be enameled through the various furnace chambers.

It is obvious, from the description of the chain assembly above described, that radiant heat from the burning chamber (in which the heat is most intense), will largely be absorbed by .the lower flanged portion of the bafiie blocks 34, and taken up by the cool air slowly forced down and seeping from above through the tortuous passages between the baffle rails and bafile plates. Inpractice, it has been found that the suspension rods 35 (which require frequent replacement) are not heated above redness for a distance of a foot or more from their upper ends, and the conveyor chain members are adequately protected from injury by heat escaping through the slot in the top furnace wall.

While the baffling blocks 34 are all arranged to engage suspension rods 35, in order to provide for spacing the latter as may be desired, it is in general found convenient to attach the rods to the blocks 16 which carry the roller supporting the chain, and to connect these rods flexibly together by means of upper and lower spacing links, 50 and 50", respectively, having overlapping looped ends engaging pivots 51 formed with upper hooks arranged to engage hooks formed on the lower ends of the suspension rods and lower hooks arrangedto engage the top cross members of the carrier boxes next to be described.

Describing first the form of box illustrated in Figs. 22 to 24, inclusive, the ends of the box consist of a pair of frames having side bars 52 (which may be made of metal tubing, flattened at top and bottom, as shown) secured to a top cross member 53, preferably formed with a. row of orifices for the engagement of suspension hooks, and to a bottom cross strip 54, which preferably extends beyond the side bars 52. A pair of such frames,

suspended from chains by the hooked pivots 51, are tied together by what I term a box tool, consisting of a frame having side members 55-55, and cross-members 56-56. The side members 55 are notched on both sides near their opposite ends (see Fig. 23), so

that when warped and bowed downwardlyby the weight of articles carried in the box under the extreme heat to which they are subjected in the burning chamber, the box tools may be inverted, the notches in either position being arranged to fit over the cross strip 54 of the carrier frames. Removable supports for the articles to be enameled, of the ordinary type illustrated in Figs. 23 and 24,

- 5757 which are constructed with bends providing seats for attachment of the ends of intermediate cross-strips 58, and having a bottom cross-strip 54, corresponding to the cross-strip 54 of the previously described form of box. The box tools above described may be engaged with either the intermediate cross-strips, or the bottom cross-strips of a pair of adjacent frames of the last described construction. 4

I have also illustrated in said Fig. 25, and Figs. 26 and 27 a form of box tool ada ted to support certain classes of articles, suc as pans and other articles having a broad flat bottom. This tool consists of a flat strip 59 having end bends adapted to hook over the cross-strips of a pair of frames, and formed with sockets arranged to loosely receive pointed flanged studs 60, whichmay be .replaced as soon as they become smeared in use with the enameling composition. At appropriate work stations between the furnace, work tables are arranged adjacent to the line of travel of the conveyor chain, dipping tables and spraying tables being arranged at both ends of each drying chamber, and one set of heading tables be1n arranged within the loop of the chain an another at its extreme left end, the position of the tables being diagrammatically outlined and designated on Fig. 1 of the drawings.

In furnaces of the type to which my invention relates it has been found that at the openings at each end of the furnace a considerable volume of heated air will continually escape at the top, and at the bottom a considerable movement of cold air into the furnace' will occur, the escape of the heated air apparently being to some extent enhanced by the heating and expansion within the furnace of the cold air entering at the bottom. Midway of the furnace opening there appears to be little movement of air either into the furnace or out of it. When there is a strong draft through the building in which the furnace is situated, it has been further observed that considerably more heat will escape at one end of the furnace than the other. In order to reduce the loss of heat and attain greater regularity in the operation of the furnace I have devised a novel draft control device which may be used at either or both ends of the furnace, or in any furnace in which similar conditions obtain. In the present instance (see Figs. 13 to 16, inclusive) this device includes a double suction box 80, which is secured to the furnace wall adjacent the top of the two furnace openings at the particular end of the furnace, and is formed with openings on its lower side adapted to draw in heated airtending to escape out of the top portion of such openings,see Figs. 15 and 16. This suction box is connected by a pipe 81 with the intake connection ofa blower 82, the outlet pressure, connection being connected by a pipe having branches 8383 connected with blower boxes 8484 secured to the furnace wall at the bottom of the furnace opening. The blower boxes are formed with draft outlets (see Fig. 17 extending across the bottom of the furnace of the furnace'openings, also connected with the blower, but in practice this is sometimes found unnecessary.

With a furnace constructed and arranged as above described a very great flexibility of operation and capacity for a great variety of work is attained. For many products a coating inside the article of one color, usually white, is employed, and an outside coating of a different color, the inside coatings being usually applied by a spraying rocess and they outside by dipping. On ot er articles a double coating, either inside or outside the article, or both, are used, and these must be separately dried but may be burned or fired together to form a fused coating on the article. In other cases a beading at an edge of the article must be applied. At each coating (or beading) operation the articles are rernoved from the carrier boxes, or the carrier .-boxes are removed and others substituted.

the tables marked Beading tables between the two reaches of the conveyor chain 1, I am enabled to transfer articles on the outer reach directly across to the inner reach. By the provision of a beading table at the left end of the apparatus, outside the loop, I am enabled to bead articles which have received two coatings, separately dried by travel through the two auxiliary drying furnaces.

It is obvious that the auxiliary furnace and table arrangement associated with conveyor chain 1, might be duplicated (in reverse order), in place of the apparatus associated with chain 2, if desired, to enlarge the total capacity of the apparatus.

Certain features directed to the construction of the conveyor chain and the carriers thereon employed for supporting articles passing through the furnace are covered in a divisional application, 449,816, filed May 5, 1930, and issued August 18, 1931, as Patent 1,819,472.

I claim:

1. In apparatus for heating enameled articles, a main furnace having enclosing walls providing consecutive drying, preheating and burning zones and a combustion chamber below said burning chamber, an auxiliary drying furnace parallel with said main furnace, a flue passage communicating with said combustion chamber and having a portion extending longitudinall through the lower part of said auxiliary furnace, and an endless conveyor chain having opposite reaches arranged to traverse said auxiliary furnace and said zones of the main furnace.

2. In apparatus for heating enameled articles, a main furnace having two separated burning chambers and double intercommunieating preheating and drying chambers severally aligned with said burning chambers and having two combustion chambers severally arranged below said burning chambers, auxiliary drying furnaces arranged on opposite sides of said main furnace parallel therewith, two flue passages severally communicating with said combustion chambers and having portions extending through the lower portions of said auxiliary furnaces, and two endless conveyor chains, each having opposite reaches arranged to traverse one of said auxiliary furnaces and the aligned burning, preheating and drying chambers of the main furnace on the side adjacent said 4 auxiliary furnace.

3. Apparatus according to claim 2 in which the combustion chambers of the main furnace severally extend under the aligned portion of the preheating chamber.

4. In apparatus for heating enameled articles, a main furnace having aligned drying, preheating and burning chambers, an auxiliary drying furnace parallel with said main furnace, means common to said furnaces for heating the same and an endless conveyor chainhaving-broadly spaced parallel reaches severally traversintgl said mam furnace and said. auxiliary mace, whereby work stations for appl the unvitrifiedenamel coating are rovid both within and without the loop the chain.

5. Apparatus according to claim 4 in which the conveyor chain is actuated by a driving a rocket at one end of the apparatus, and at e opposite said chain engages a series of link conveyor arranged to run within said hood, means for forcin cold air into said hood, and means for b 'ng the circulation 1 of air between said hood and said slot insuch passage through its tglp rtic a clud' bafilmg' members secured to the conve oi' Iinks and extending into said slots.

In a paratus for heating enameled articles, a ace-having a burning passage and formed with a narrow slot extending from such passage through its top wall, a hood overlying said slot, and articulated metal-link conveyor arranged to run within said hood, means for forcinigold air into said hood, and means for ba g the circulation of air between said hood and said slot including flanged baflling blocks pivoted to the conveyor hnks.

8. In apparatus for heatin enameled articles, a furnace having a burning passage and formed with a narrow slot extending from wall, a hood overlying said slot, an a ted metal-link conveyor arranged to run within said hood, means for forcing cold air into said hood, and means for baflling the circulation of air between said hood and said slot including baffling blocks pivoted to the conveyor links and formed with top and bottom flanges, the upper-fla being cut back on one block and extend on-the adjacent block to lap the joint between the bodies of the blocks.

' 9. In apparatus for heating enameled articles, a furnace having a burning passage and formed with a narrow slot extending from such passage through its top wall, a

hoo ov ly ng d o :11 ar imllat m -l n nvey am d t 1 1 w hin said hood, Ineansfor for, cold air into said hood, and means for b 'n'g the circus lation of air between said hood and said slot includil-nlgk baflling blocks pivoted to the connd form with p an b t m vey r fla ge and baflling mil eated in h f rnace wall at the opposite up redgesofthe .slot therethrough, said 'b 'ng rail beirag formed with opposite vertical in'ner faces a jacent the edges of the top flanges of the blocks and with'bottom portions extending inwardly between the planes of the top an bottom flanges. I

10. In apparatus .for heating enameled articles, a furnace having a burning passage and formed'with a narrow slot extending from such passage through its top wall, a hood overlying said slot, an articulated met.- al-link conveyor arranged to run within said hood, means for forcinfild air into said hood, and means for ba the circulation of air between said hood an said slot includinngksbaflling blocks pivoted to the conveyor 1i said blocks being vertically orificed, and hooked sus nsion rods engaging the orifices in saidb ocks.

11. An enameling furnace comprising enclosing walls for two groups of zones aring, burning and cooling zones, a wall between said burnin 'zones to permit the maintenance of di erenttemperaturestherein,apair of-conveyors each having a reach passing through one of said groups of zones, and-an auxihary drying furnace through which the other reach of one of said conveyors passes.

13. In apparatus for heating enameled arrangeld consecutively from opposite ends of ticles, a main furnace having enclosing'walls providing consecutive drying, re-heating and burmng zones an aux liary drying furnace associated with said mam furnace, a conveyor chain having opposite reaches arranged to traverse said auxiliary furnace and sai zones of said main furnace; and a driving sprocket exterior-of said furnaces for actuating said chain.

In testimony whereof, I have subscribed my name.

ROBERT MacDOUGALL.

CERTIFICATE OF CORRECTION.

Patent No. 1,857,206. May 10, 1932.

ROBERT MacDOUGALL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 5, line 93, claim 1, for "chamber" read zone: and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Sign d and sealed this 14th day of November, A. D. 1933.

F. M. Hopkins (Seal) Acting Commissioner of Patents. 

